The National Academies

NCHRP 14-26 [Final]

Culvert and Storm Drain System Inspection Manual

  Project Data
Funds: $250,000
Research Agency: Simpson Gumpertz & Heger, Inc.
Principal Investigator: Mr. Jesse L. Beaver
Effective Date: 8/24/2012
Completion Date: 5/31/2016

The agency’s final report presents a new manual for assessing the condition of in-service culvert and storm drain systems to ensure safety, performance, and the economical use of owner resources. The new manual includes: (1) a catalog for distressed conditions with photographic reference, (2) inspection techniques, (3) condition assessment and numerical rating criteria, (4) inspection reporting, and (5) best practices to help agencies manage their culvert inventory. The material in this report will be of immediate interest to culvert and storm drain system owners and inspectors.

The Federal Highway Administration (FHWA) developed a comprehensive program in 1986 to address the global need to identify, quantify, and rate culverts. The end product was the FHWA Culvert Inspection Manual. The 1986 manual has seen widespread use as the basis for DOT and local agency culvert inspection programs, but has not been updated to reflect important industry changes such as new pipe types, culvert design for alternate uses, evaluation of storm drains, and advanced inspection techniques. There is a critical need to develop an updated publication to incorporate these changes. The new manual developed in this research addresses new pipe products including materials (e.g., plastic pipe), coatings, and rehabilitative linings and less common materials such as timber. These added products required the inclusion of new inspection guidelines and procedures for both culverts and storm drain systems. Facilities designed to accommodate aquatic organism passage (AOP), specifically open-bottom shapes and embedded closed-bottom culverts, are becoming a national focus and needed more detailed descriptions for inspectors than that found in the 1986 manual.  In addition, the new manual covers elements of storm drain systems including: closed inlets, junctions, manholes, and energy dissipaters. The new manual also provides guidance to inspectors on remote access inspection techniques such as digital camera and laser-ring technologies for assessing restricted-access pipes.


This research was performed under NCHRP Project 14-26 by Simpson Gumpertz & Heger, Inc., to develop an inspection manual for assessing the condition of in-service culvert and storm drain systems. The Culvert and Storm Drain System Inspection Manual will be published by AASHTO in fall of 2019.

NCHRP held a workshop at the 2018 National Hydraulic Engineering Conference on August 28, 2018. The workshop presentation is available at:


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